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Low End (low + end)
Selected AbstractsCo-occurrence of ectoparasites of marine fishes: a null model analysisECOLOGY LETTERS, Issue 1 2002Nicholas J. Gotelli We used null model analysis to test for nonrandomness in the structure of metazoan ectoparasite communities of 45 species of marine fish. Host species consistently supported fewer parasite species combinations than expected by chance, even in analyses that incorporated empty sites. However, for most analyses, the null hypothesis was not rejected, and co-occurrence patterns could not be distinguished from those that might arise by random colonization and extinction. We compared our results to analyses of presence,absence matrices for vertebrate taxa, and found support for the hypothesis that there is an ecological continuum of community organization. Presence,absence matrices for small-bodied taxa with low vagility and/or small populations (marine ectoparasites, herps) were mostly random, whereas presence,absence matrices for large-bodied taxa with high vagility and/or large populations (birds, mammals) were highly structured. Metazoan ectoparasites of marine fishes fall near the low end of this continuum, with little evidence for nonrandom species co-occurrence patterns. [source] Physical properties of Martian meteorites: Porosity and density measurementsMETEORITICS & PLANETARY SCIENCE, Issue 12 2007Ian M. COULSON These samples represent igneous rocks, much like basalt. As such, many laboratory techniques designed for the study of Earth materials have been applied to these meteorites. Despite numerous studies of Martian meteorites, little data exists on their basic structural characteristics, such as porosity or density, information that is important in interpreting their origin, shock modification, and cosmic ray exposure history. Analysis of these meteorites provides both insight into the various lithologies present as well as the impact history of the planet's surface. We present new data relating to the physical characteristics of twelve Martian meteorites. Porosity was determined via a combination of scanning electron microscope (SEM) imagery/image analysis and helium pycnometry, coupled with a modified Archimedean method for bulk density measurements. Our results show a range in porosity and density values and that porosity tends to increase toward the edge of the sample. Preliminary interpretation of the data demonstrates good agreement between porosity measured at 100× and 300× magnification for the shergottite group, while others exhibit more variability. In comparison with the limited existing data for Martian meteorites we find fairly good agreement, although our porosity values typically lie at the low end of published values. Surprisingly, despite the increased data set, there is little by way of correlation between either porosity or density with parameters such as shock effect or terrestrial residency. Further data collection on additional meteorite samples is required before more definitive statements can be made concerning the validity of these observations. [source] Does Size Really Matter?PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 6 2008A Comparison of the Riata Lead Family Based on Size, Its Relation to Performance Background: Recently, the performance and safety of smaller diameter implantable cardioverter defibrillator (ICD) leads has been questioned. The purpose of this analysis was to determine the impact of size on lead performance and perforation rates by comparing the performance of 7 French (7F) and 8 French (8F) leads with similar design characteristics implanted by a single operator. Methods: Patients implanted with a Riata 1580 (8F) or 7000 (7F) series leads (St. Jude Medical, Sylmar, CA, USA) over a 2-year period were evaluated to compare performance and perforation rates. Results: There were 357 Riata 8F leads and 357 Riata 7F leads implanted in 714 patients. Follow-up ranged from 1 to 24 months. The 8F leads were implanted in the right ventricular apex more often than were 7F leads (129 or 37% vs 72 or 20%, P < 0.0001). Oversensing that did not result in therapy occurred in 2 pts (0.56%) with 8F leads and 1 pt. (0.28%) with a 7F lead (P = 0.56). Oversensing with therapy occurred once in both groups (0.28%, P = NS). One perforation occurred in each group (0.28%, P = NS). Both occurred in leads that were implanted in the right ventricular apex (P = 0.02). Conclusions: The performance of St. Jude Medical 7F and 8F Riata leads was similar. The incidence of lead-related adverse events was within or below the low end of published acceptable ranges for ICD lead perforation and sensing anomalies. Perforations were less likely to occur in leads that were implanted in nonapical positions. [source] A Safe and Cost-Effective Short Hospital Stay Protocol to Identify Patients at Low Risk for the Development of Significant Hypocalcemia After Total ThyroidectomyTHE LARYNGOSCOPE, Issue 6 2006Zayna S. Nahas BS Abstract Objective: The objective of this retrospective chart review was to determine if serial postoperative serum calcium levels early after total thyroidectomy can be used to develop an algorithm that identifies patients who are unlikely to develop significant hypocalcemia and can be safely discharged within 24 hours after surgery. Methods: Records of 135 consecutive patients who underwent total/completion thyroidectomy and were operated on by the senior author from 2001 to 2005 have been reviewed. For the entire study group, reports of the early postoperative serum calcium levels (6 hours and 12 hours postoperatively), final thyroid pathology, preoperative examination, inpatient course, and postoperative follow up were reviewed. An endocrine medicine consultation was obtained for all patients while in the hospital after surgery. For patients who developed significant hypocalcemia, reports of their management and the need for readmission or permanent medications for hypoparathyroidism were reviewed. According to the change in serum calcium levels between 6 hours and 12 hours postoperatively, patients were divided into two groups: 1) positive slope (increasing) and 2) nonpositive (nonchanging/decreasing). Results: All patients with a positive slope (50/50) did not develop significant hypocalcemia in contrast to only 59 of 85 patients (69.4%) with a nonpositive slope (P < .001, positive predictive value of positive slope in predicting freedom from significant hypocalcemia = 100%, 95% confidence interval = 92.9,100). In the nonpositive slope group, 61 patients had a serum calcium level ,8 mg/dL at 12 hours postoperatively (,0.5 mg/dL below the low end of normal), and 53 (87%) of these patients remained free of significant hypocalcemia in contrast to only 6 (25%) of 24 patients with serum calcium level <8 mg/dL at 12 hours postoperatively (sensitivity = 90%, positive predictive value = 87%). In addition, of the eight patients who developed significant hypocalcemia in the nonpositive slope group with a serum calcium level ,8 mg/dL at 12 hours postoperatively, 7 (88%) patients developed the signs and symptoms during the first 24 hours after total thyroidectomy. Readmission and permanent need for calcium supplementation happened in two patients, respectively, all with serum calcium levels <8 mg/dL at 12 hours after total thyroidectomy. The compressive and/or symptomatic large multinodular goiter as an indication for thyroidectomy was associated with developing significant hypocalcemia (P < .05). There was no statistically significant correlation between the development of significant hypocalcemia and gender, age, thyroid pathology other than goiter, or neck dissection. Conclusion: Patients with a positive serum calcium slope (t = 6 and 12 hours) after total thyroidectomy are safe to discharge within 24 hours after surgery with patient education with or without calcium supplementation. In addition, patients with a nonpositive slope and a serum calcium level ,8 mg/dL at 12 hours postoperatively (,0.5 mg/dL below the low end of normal) are unlikely to develop significant hypocalcemia, especially beyond 24 hours postoperatively, and therefore can be safely discharged within 24 hours after total thyroidectomy with patient education and oral calcium supplementation. Our management algorithm identifies those patients at low risk of developing significant hypocalcemia early in the postoperative course after total thyroidectomy to allow for a short hospital stay and safe discharge. [source] Patterns and gradients of diversity in South Patagonian ombrotrophic peat bogsAUSTRAL ECOLOGY, Issue 1 2010TILL KLEINEBECKER Abstract Many north-hemispherical mires seemingly untouched by drainage and cultivation are influenced by a diffuse sum of man-made environmental changes, such as atmospherical nitrogen deposition that mask general patterns in species richness and functional group responses along resource gradients. To obtain insights into natural diversity-environment relationships, we studied the vegetation and the peat chemistry of pristine bog ecosystems in southern Patagonia along a west,east transect across the Andes. The studied bog ecosystems covered a floristic gradient from hyperoceanic blanket bogs dominated by cushion building vascular plants via a transitional mixed type to Sphagnum -dominated raised bogs east of the mountain range. To test the influence of resource availability on diversity patterns, species richness and functional groups were related to environmental variables by calculating general regression models and generalized additive models. Species richness showed strong linear correlations to peat chemical features and the general regression model resulted in three major environmental variables (water level, total nitrogen, NH4Cl soluble calcium), altogether explaining 76% of variance. Functional group response illustrated a clear separation along environmental gradients. Mosses dominated at the low end of a nitrogen gradient, whereas cushion plants had their optimum at intermediate levels, and graminoids dominated at high nitrogen contents. Further shifts were related to NH4Cl soluble calcium and water level. The models documented partly non-linear relationships between functional group response and trophical peat properties. Within the three bog types, the calculated models differed remarkably illustrating the scale-dependency of the explanatory factors. Our findings confirmed several general patterns of species richness and functional shifts along resource gradients in a surprisingly clear way and underpin the significance of undisturbed peatlands as reference systems for testing of ecological theory and for conservation and ecological restoration in landscapes with strong human impact. [source] Energy substrate production in infants born small for gestational ageACTA PAEDIATRICA, Issue 1 2007Barbro Diderholm Abstract Aim: To investigate energy substrate production and its hormonal regulation in infants born small for gestational age. Methods: Eleven infants, aged 24.4 ± 5.3 hour, were studied following a fast of 4.0 ± 0.6 hour. Gestational age was 35.4 ± 2.8 weeks and birth weight 1804 ± 472 g (<,2 SD). Rates of glucose production and lipolysis were analyzed using [6,6- 2H2]-glucose and [2- 13C]-glycerol. Results: Plasma levels of glucose and glycerol were 4.1 ± 1.1 mmol . L,1 and 224 ± 79 ,mol . L,1, respectively. Glucose appearance averaged 30.3 ± 8.2 and glucose production rate 21.1 ± 6.1 ,mol . kg,1 . minutes,1. Glycerol production rate was 5.6 ± 1.6 ,mol . kg,1 . minutes,1, correlating strongly to birth weight (r = 0.904, p < 0.001). Of the glycerol produced, 55 ± 22% was converted to glucose, corresponding to 8 ± 3% of the glucose production. Conclusions: Even though the infants could produce energy substrates, lipolysis was reduced and the glucose production was in the low end of the normal range compared with infants born appropriate for gestational age. The correlation between glycerol production and birth weight indicates that lipolysis depends on the amount of stored fat. Data on insulin and insulin-like growth factor binding protein 1 support the view that insulin sensitivity in these infants is reduced in the liver but increased peripherally. [source] Effect of Oscillating Sheath on Near-Wall Electron Current Profile in Hall ThrustersCONTRIBUTIONS TO PLASMA PHYSICS, Issue 9-10 2008D. R. Yu Abstract The radial profile of the axial electron current in Hall thrusters was measured; however, the significant decay of the current density peak in the near-wall region can't be explained effectively by the steady sheath theory. As the sheath exhibits an oscillating character when the thruster is in operation, its effect on the near-wall current profile has been studied in this paper. To obtain a comprehensive knowledge, we have considered a wide sheath oscillation frequency span which includes two asymptotic frequency cases at high and low ends. Based on the case studied, either an analytical treatment or a numerical simulation is applied. The results show that the current density peak has a fastest damping speed away from the wall at the asymptotic low frequency. With the increase of the frequency, both the decay and the spatial "wavelength" of the current profile decrease. The decay finally disappears at the asymptotic high frequency with a constant spatial "wavelength". Moreover, the sheath oscillation amplitude can enhance the decay and enlarge the spatial "wavelength". Taking into account of the realistic situation in Hall thrusters, the significant impact of the oscillating sheath on the near-wall electron current profiles can be anticipant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Measuring conscientiousness and professionalism in undergraduate medical studentsTHE CLINICAL TEACHER, Issue 1 2010John McLachlan Summary Background:, There is gathering evidence that concern about professionalism expressed by staff with regard to undergraduate medical students represents a statistically significant risk factor for referral for disciplinary action in later clinical practice. But, ,professionalism' as a concept is variously defined, and is generally seen as difficult to measure. This is because such measures are usually highly subjective, and take place on limited numbers of occasions. We are interested in hints from the literature that a significant part of professionalism is what might be thought of as diligence or conscientiousness. Methods:, We award students points on every occasion when they might be conscientious in performing simple tasks (such as attending compulsory sessions, providing essential documentation and participating in required administrative procedures). This is aggregated over the year to give a continuous, objective and multi-occasion score that is inexpensive to construct. We then determine the relationship of this score with independent staff and student estimates of professionalism. Results:, We observe a positive correlation between conscientiousness and professionalism at both high and low ends of the spectrum. Discussion:, This correlation raises a number of further questions. What is the sensitivity and specificity of this measure? How might it best be used with students: as a formative tool to change behaviours or as a summative tool to affect progression? And how will students react to its use? Finally, can it be extended to spheres other than undergraduate education, for instance with postgraduate trainees? [source] | ||||||||||||||||